Blasting cartridge



June 21,1927. 1,632,887

J. H. CRAWFORD ET AL BLASTING CARTRIDGE Original Filed May 5. 1924 ram-ed 111M 21, 1927. i

UNITED"STAT ES PATENTOFFICE.

JOHN H. cmwronn, ARTHUR w. HELMHOL'IZ, m 1mm rmmm, or m,

rumors, ASSIGNORS no man rnnssunn mums & comma comm, or museum, rumors, A conrom'rron orrumors.

V ms'rnwe can'rnmen.

' HEISSUED Application mm Inn, 19241 Serial 10. 11am. Renewed December 1:, 1m.

This invention relates to, a new andima plosives have a number of drawbacks. Their' explosive force is applied so rapidly that a large portion of the coal brought down 15 pulverlzed leaving a comparatively small percentage of lump coal. A further objec 15 tion lies in the fact that dangerous gases are generated by the explosion. Also there is danger that the flame of the explosion will ignite mine gases, with serious results. It has been heretofore proposed that liquid air or oxygen be used as a means for blasting,but they have been used in combination with combustible substances in the endeavor to cause rapid combustion. It has also been proposed to confine-a liquid gas such as oxygen or air in a closed receptable or container which is tamped into a bore hole in rock or coal seams. The liquid gas is expected to absorb heat from the surrounding walls suificient for vaporization of the liquid gas, which is to generate enough pressure to burst the container and so act as an explosive cartridge.

The use of gases of this type is open to many serious objections. The critical temperature of-liquid air is 140 centigrade and of liquid oxygen 118 centigrade. Consequently these gases are very expensive to liquefy and must be handled-in vacuum bottles. The loss by evaporation is very great since their critical temperatures are so low that they are always vaporizing at usual atmospheric temperatures.- To confine such gases in closed receptacles and handle'them in normal mine temperatures would be extremely dangerous.

According to the present invention. carbon dioxide is used in its liquid and solid state for purposes of explosion. Other gases having critical temperatures above normal mine temperatures may be used. Carbon dioxide has a critical temperature-of +31.1 centigrade or approximately 88" Fahrenheit which assures that it will remain in its liquid state at temperatures normally enlosses such as are incident to the use of liquid similar'weight of black pow er. plosive force generated may be controlled s is therefore in closed contamers while in the iquid or solid state without danger of rupture of the container. Consequently there are no evaporation air or oxygen. p

The explosive force of li uid or solid carbon dioxide when gasified y the appli-- cation of heat is substantiall equal to a Theexwithin narrow and well defined limits by controlling theibursting strength of the container or rupturable portion of. the container and by controlling the amount of heat applied. Such a'control is possible by virtue of the fact that the nature of the expansion of the carbon dioxide is entirely difi'erent from ordinary explosives. Any of the ermissible explosives rely essentially on t eir great heat of combustion, due to their exothermic action that takes place, tofexpand the gas formed by the reaction, whereas the entire expanding of the carbon dioxide as I described in this application is due to the application of heat from some external source, the term external source meaning that other than by an exothermic reaction, and means one which can be accurately controlled as desired. With this feature clear in mind when considered with the feature of providing a wall rupturable at a definite predetermined pressure, it can be readily understood that the expanding of the gas can be accurately controlled at the time of release without relying entirely on the amount of expanding substance employed. The gas is non-combustible and hence when used there is no danger of ignition of coal dust or gas. The instant explosion of the gas on the release of pressure uponthe container causes a cooling effect, thus dissipating the heat supplied and damping any combustion effect which might be given by the heated receptacle. The quantity of carbon There is a decided difference between the explosion of common explosives and that of a cartridge produced according to the principles of our invention, wh ch difference has a very important bearing on thelr utility in connection with use for mine blasting. It is found that ordinary GXPlOSIVQS when set off expand with such rapid violence with forces imparted in all directions with the result that when these explosives are used in mine blasting, they cause a destructive effect on" coal broken away from the wall of the mine and aconsequent powdering of a large ercentage of the coal yield. Inasmuch as t is is an undesirable result as it renders so much of the coal mined second grade coal, it is desirable to provide a method of extracting coal by blast which will be free from this objection. Cartridges constructed according to our invention containing carbon dioxide as are found to have the effect when exp oded of breaking from the walls of the mine large quantities of coal in large lumps and free from the objectionable powder. This is attributable to the action of the substance which is not a liquid at ordinary temperature and pressure and which seeks a gaseous state under these conditions when liberated, as by the bursting of one rupturable wall of the cartridge and the releasing of the expanded gas in an inward direction only relative to the wall of coal. Ordinary explosives rely usually for theirefiect in the expanded condition of the gases due to the tremendous heat of combustion created during the explosion of the shell but which decrease in their forcing eflect with a decrease in the temperature. Contrary to this action, substances which are gaseous at ordinary temperatures and pressures and which are forced to seek a gaseous state when in a confined area will not lose their forcing power as do ordinary explosives, for the reason that they do not rely upon high temperatures for their maximum eflect. The action of carbon dioxide gas when liberated from a liquid state under pressure will be that of a comparatively slow and positive forcing or expanding action with the result that a large mass of coal is literally pushed outwardly from the wall of, the mine without the detrimental crumbling or powdering of large portions instant to ordinary blasting operations. To this end, animproved cartridge has been formed which utilizes very efficiently this peculiar behavior of gases of this type, which embodies a cartridge container having one rupturable wall which forms the closing-wall of the tubular containin member which acts to direct the explode gases in a single direction, wardly toward the inner end of the drill hole. It is found that confinin the expanding action of the gases to t at of an provide which direction is ininward direction will result in a very ellicient breaking action of a large mass of coal while maintaining the coal in large lumps.

It is important in constructing this cartridge to provide for a special combination of elements and provide for the details of construction as these effects materially the behavoir of the explosion when the cartridge is set off. Carbon dioxide is a very poor conductor of heat and it is on this account that it is necessary to embody several particular features of construction in this cartridge. One of these features is the selection of a closed container which will give vent to the expanding gases in a given direction and only when a definite redetermined pressure has ben reached. e pressure established within the cartridge is dependent u n the two factors, namely, the amount 0 gas compressed in the limited volume of the container, and to the heat to which this compressed gas is subjected. The predetermined pressure mentioned above is so selected relative to the quantity of carbon dioxide contained in the shell that it is necessary to effect a substantial heating of the entire volumeof the gas instantaneously in order that the critical temperature of the liquefied gas will be reached. In view of the fact that the contained liquid is a poor conductor of heat, it is necessary to a heating device which will serve to heat instantaneously every particle of the liquid throughout the entire volume contained in the cartridge without relying on liquid to conduct heat to remote portions of its volume. If the heating action does not extend to the entire volume as described above, the quantity of liquid selected for a given cartridge as efiecting an increase of pressure in the heating action will not be sufficient to overcome the resistance of the rupturable Wall of the container with the result that the cartridge is not exploded. T e result of the combination of these various features produces a very efficient and desirable result for the reason that the greater expanding and forcing action is accomplished by the instantaneous increase in pressure with a consequent yielding action of the container wall when this pressure is reached. The most important feature for producing this result is the rapid dissemination of heat to every voulme in connetcion with the instantaneous yielding of the container Wall when this particular pressure is reached.

It is an object of the present invention to provide a new and improved means and" portion of the liquid recess? directed to expand upon being released in one direction only.

It is a further object to provide m'eans and method of this character which generate no flame and no noxious see.

It is an additional ob ect'to provide means and method which can be carried out bycomparatively simple cartridges applied in the usual size of drill holes and capable of manufacture at small cost.

Other and further objects will appear as the description proceeds.

a We have illustrated in the accompanying drawings certain preferredembodiments of our invention.

In the drawings:

Figure 1 is one modification of our device, shown in cross section of a side ole-- vation;

Figure 2 is a similar view except that it is partly in cross section and of a slightly modified form.

Referring to the figures, with s cial reference to Figure 1, it will be note that our invention-embodies a casing 41 having a a closed end 42 The closure disk'43 is held source of current supply 48.

in place by the overhanging flange 44 of the screw cap45. Secured to the disk and extending inwardly therefrom is the container 46 adapted to contain any suitable explosive which is exploded by the application of heat. The resistance wire 47 surrounds only that portion of the casing which contains the explosive cartridge 46, which resistance wire-is connected to the The form of construction shown in Fig "ure 2 is similar to that shown in Figure 1.

In this case, however, the explosive cartridge 51 is sup onator 52 and t llS detonator is connected by wires 53and 54 with the source of current supply 55.

n the 7 shown, oneend wall of the tube 41 is closed by metal disc 43 which ruptures at a predetermined pressure, which pressure, however, is considerably less than the strength of the body of the casing 11, When the disc 43 is broken away, this end of the con-' tainer'constitutes the only opening through which the gas can expand with the result that the entire expanding force is directed in the direction of the application of this end ,of the cartridge.

When the device shownin Figure 1 is set ofl', the entire casing 46 will be blown out with the central portion of the closure 43. A newcasing is put in place with the the casin with the .cartri ge 46 new closure after fillin liquid. The contents may be an suitable explosive which is adapted toexploded by the application of heat. This explosive may beapplied at the mine shortly before the use of the carlied with the electrical det-'.'

use of both forms. of cartridges to fire shots only between shifts.

be necessary tridge. The heat is electric current throu the resistance wires .47 and this heat has only be suflicientrto explode the explosive in the cartridge 46. The exgllosion of this explosive generates heat su cient to gasify the liquid or solid in the receptacle which causes secondary explosive action, which ruptures the closure 43. It will be understood that the primary explosion of the material in the cartridge 46 will not be of. suflicient force to rupture the closure 43. Practically the two explosions I will usually be substantially simultaneous.

The form of easing shown in Figure 2 is filled in a similar manner as that shown in Figure 1. The operation of this form of construction diflers merely in that the-explosion in the cartridge 511s set of! by means of a small electrically operated detonator 52. This detonator operates instantaneously and the explosion of the material in the cartridge 51 generates heat suflicient to gasify the entire volume of the liquid or solid gas in the container instantaneously gfnerated by passing cause the gasifying action which results in the desired explosive eflect. In practicing this invention 1n all forms, it is to be understood that the value of this device resides in the combination of this type of expanding gas with suitable heating apparatus, together with a container having its inner wall rupturable at a predetermined pressure so that-the expanding charge is concentrated in an inward direction into the drill hole when set off so as to directthegasinto the fissures between the seams of coal where it expands and influences a wedging action to break the coal away from the mine wall. The term inward direction as found in the, appended claims means the direction into the wall of coal and toward the inner end of the drill hole.

All of the forms shown are simple in design and construction and may be chea l manufactured. They may be used repeate ly and can be refilled for such use without expensive apparatus. These cartridges may be fitted in usual sizes of drill holes and consequently require no modification of other mine machinery.

With the use of our explosive method and means, a large number of falls of coal can be made per day as it will we contemplate such further modifications as may come within the spirit and scope of the appended clalms.

We claim 5 1. A blasting cartridge compjrising a rigid oxide to and above the critical temperature 15 of the non-gaseous carbon dioxide.

a 2. A blasting cartridge comprising a cylindrical casing, one end of the casing bein v adapted to be ruptured by: a predetermined pressure in the casing, a charge of carbon dioxide in the non-gaseous state in the casing and electrically controlled means for raising the carbon dioxide to and above its critical temperature whereby the carbon dioxide will become gasified and will rupture the end wall of the casing to release the con- 35 tents in an inward direction only.

Signed at Harrisburg, Illinois, this 29 day of April; 1924. v

JOHN H. CRAWFORD. A. w. HELMHOLTZ. DENT FERRELL. 

